The invention relates generally to seed planters for dispensing individual seeds at a controlled rate into a seed furrow, and in particular, to a device and corresponding method for metering seeds at a desired rate.
Modern row crop planters or seed planters include multiple row planting units attached to a toolbar and towed behind a tractor. Each of the row planting units are responsible for opening a seed trench or furrow, dispensing the seeds into the furrow, then closing the furrow after the seeds are planted. The seed furrows are opened by a first pair of discs extending down from the planter at its leading end, closed by a second pair of discs extending down from the planter at its trailing end, and then tamped down by a trailing wheel which follows both disc pairs.
Typically, each row planting unit has its own seed hopper and seed metering system for dispensing the seeds at a controlled rate into the seed trench or furrow as the planter advances along the ground. The most common seed metering systems are vacuum-type meters that use vacuum force to draw air through multiple openings in a rotating seed disc, trapping individual seeds within each opening for delivery to a second location for their release to a seed placement device. The individual seeds are then delivered by the seed placement device, between the furrow opening disc and the furrow closing discs, into the open furrow at a controlled rate.
To perform the various seed metering operations, conventional row crop planters utilize a vacuum typically provided by a blower driven by a hydraulic motor attached to the hydraulic system of the tractor. However, the force required to rotate the seed disc is typically provided by a ground drive or a hydraulic drive. The ground drive, hydraulic drive, or other power source rotates a main, common driveshaft extending substantially the entire width of the row crop planter. The individual seed metering systems of the individual row planting units take power from this main driveshaft. The power is transmitted from the main driveshaft to the individual row planting units by way of chain or cable drives, driving a meter driveshaft, whereby the meter driveshaft serves as a power accepting jackshaft.
Typical meter driveshafts extend axially from, and concentrically drive, the seek disk. Some attempts have been previously made to improve the compactness of seed metering systems by moving the meter driveshaft from a concentric drive interface to a perimeter drive interface. Known perimeter drive systems still rely on a main driveshaft serving as a common power source for all the row planting units within a row crop planter. Although such previous perimeter drive units may improve compactness of seed metering systems to some extent, they fail to address numerous issues associated with operational uniformity of seed metering systems.
In modern farming practices, there is an increased reliance upon precision planting methods. Correspondingly, the integrity of modern seed metering system operations are closely related to system efficiency, consistency, accuracy, repeatability, and thus uniformity in placing seeds during use. Known seed metering systems, concentric drive and perimeter drive alike, face various performance uniformity issues related to the operation of conventional main, common driveshaft and meter driveshaft linkages. For example, the torque required to drive all of the seed metering systems by a common main driveshaft can be significant, since each seed metering system can experience high levels of friction during operation as, e.g. the vacuum force pulls the seek disk toward and into contact with the meter housing. As another example, non-uniform operation can result from non-desired rotational drive speed variations realized at the meter driveshaft as the chains and/or cables flex, relax, tighten, and slacken as the row crop planter traverses somewhat irregular field surfaces. Any of these and other operating characteristics can lead to erratic seed placement.
Additionally, typical seed planters do not have the ability to deactivate individual row planting units, independently of one another. This can lead to overseeding or overplanting, dispensing more seed than needed, during various instances in which portions of the seed planter passes over a segment of the field more than once. Such instances include those in which point rows are commonly utilized, such as while working fields having irregular shapes, or fields with trees or other obstacles therein. Other such instances include various field turn areas such as turn rows, headland rows, or end rows. Some efforts have been made to deactivate individual row planting units. However, such efforts require the use of complex assemblies, for example, pneumatic clutch assemblies with numerous parts and which can require relatively large amounts of energy to operate.
There is a need for a seed metering system that provides improved uniformity of seed placement during row crop planting. There is also a need for a seed metering system that reduces the number of moving parts and complex mechanical linkages in a seed planter. Furthermore, there is a need for seed planters which include multiple seed metering systems which can be activated and deactivated independently of each other so that individual row planting units can be engaged or disengaged independently as desired, whereby overplanting can be managed and minimized.